This invention relates generally to railroad crossing and wayside signals, and more particularly a method and apparatus for monitoring the operational status of the railroad crossing signal.
Railroad systems include wayside equipment such as switches, signals, and vehicle detectors including hot wheel detectors, dragging equipment detectors, high/wide load detectors, vehicle identification systems, etc. Such equipment must necessarily be located throughout the railroad system, and is thus geographically dispersed and often located at places that are difficult to access. Systems are currently in use for communicating operational and status information relating to the condition of the train or the track to control centers through various types of modems. For example, position indicators are provided on switches and a signal responsive to the position of a switch is communicated to a control center for that section of track.
Grade crossings where streets and railroad tracks intersect are provided with various types of warning systems and/or indicators that are used to alert pedestrians and roadway vehicle operators to the presence of an oncoming train. Passive warning systems include signs and markings on the roadway that indicate the location of the crossing. Active warning systems include the audible signal from a locomotive horn as well as various types of wayside warning devices, which are activated as the train approaches. The grade crossing warning devices may include visual and audible alarms as well as physical barriers. A typical crossing in an urban area may include signs painted onto the roadway and/or erected at the crossing and a fully automatic gate device with flashing lights and bells for blocking all lanes of roadway traffic.
Regular monitoring and maintenance of the grade crossing warning systems and equipment ensures proper operation of the device. Moreover, the Federal Railroad Administration mandates regular and periodic inspection of railroad-highway grade crossing warning systems. In order to perform such tasks, routine maintenance and inspections are performed on grade crossing warning equipment. In order to conduct such inspections an inspector will visit the site of each crossing periodically to inspect the equipment and to confirm its proper operation. In order to assist in the monitoring and maintenance of these systems remote or automatic sensing devices may be employed to provide signals indicative of the operation status of the system. Examples of such systems and devices are found in U.S. Pat. Nos. 6,222,446 and 6,688,561 and U.S. patent application Ser. No. 10/248,120 the contents of which are incorporated herein by reference thereto.
One of the items of the grade crossing warning equipment requiring monitoring is the operational status of the warning lights. In order to detect the operation status of the warning light a sensor or photo sensor is positioned to measure the output of the warning light. However, the location of the sensor or photo sensor may cause the sensor to be exposed to environmental conditions that may affect the accuracy of the sensor output. Furthermore, and in order to not block the light output while also measuring the same the sensor may be positioned such that it will detect a non-uniform light signal (e.g., the sensor is not centrally located with respect to the light).
The development of an external sensor for monitoring the output irradiance of a railroad crossing flashing light must consider the influence of ambient sunlight. Direct solar rays may be reflected off the ground or lamp face (i.e., lens or roundel) and detected by a photo sensor. This reflected sunlight may lead to saturation of the photo sensor. Saturation would preclude the quantification of flashing light output irradiance and reduce the availability of the photo sensor. Accordingly, it is desirable to provide a method and apparatus for monitoring the operational status of the railroad crossing signal, which accounts for environmental conditions as well as sensor position.